I remember these very well from when my kids were little. At first they looked like they would work well. They are easy to figure out and get over a door knob. They latch together. I will say that they are a bit of a pain to use. These do not fit right around some door knobs. Some open easily by pushing in the side buttons and some don't. I found these to be pretty easy to just pull apart. It was so easy that my little one figured it out at a young age. These didn't stay on very long. What is the point of having a safety product that your child can figure out how to get past? These are not as thought out as they possibly could have been. I wouldn't buy these again. Effectiveness They are not very effective. It might work for some kids, but others will figure it out. Sometimes I found it annoying to try to open doors with them on. Safety I don't find these to be very safe when a baby/toddler can come along and just pull it apart and off of the door knob. Durability These are not very durable. They come apart too easily.